Field of the Invention
The present invention relates to polyamide resin compositions and molded articles.
Description of the Related Art
Polyamide resins have high mechanical properties (such as mechanical strength, rigidity, and impact resistance), toughness, heat resistance, and chemical resistance, and have been used in various industrial fields such as clothing materials, industrial materials, vehicles, and electrical and electronic apparatuses and devices, and other industrial fields.
In particular, polyamide resins have higher heat aging resistance than that of other resins, and are suitably used as materials for parts which receive a significantly large amount of heat, such as parts for engine compartments of vehicles.
The environmental temperatures inside the engine compartments of vehicles have been increased recently in connection with higher density of parts for engine compartments of vehicles and higher outputs of engines. For this reason, a polyamide resin which can maintain significantly higher heat aging resistance for a longer period of time than those of the traditional polyamide resins has been required.
One of the traditional techniques of enhancing the heat aging resistance of the polyamide resins is addition of a copper compound (oxide or salt of copper) and a halogen compound.
Among the halogen compounds, an iodine compound is typically added. A technique of compounding a polyamide resin, a copper compound, an iodine compound, and an aliphatic carboxylic derivative is known (for example, see Japanese Patent Laid-Open No. 7-18176).
Unfortunately, iodine as a resource is mined from the ground, and its efficient mining areas are limited. These have been increasing the cost of iodine compounds recently, and thus use of iodine compounds in polyamide resins has a problem of increased production cost.
In contrast, bromine as a resource can be extracted from sea water or the like, and is more inexpensive and industrially useful than iodine. For this reason, other techniques of adding a bromine compound rather than an iodine compound have been developed to enhance the heat aging resistance of the polyamide resin (for example, see International Publication No. WO 2013-143858 and National Publication of International Patent Application No. 2011-511097).
Unfortunately, bromine compounds are more readily corrode metals than iodine compounds. If polyamide resin compositions containing a bromine compound are used as materials for parts for engine compartments of vehicles and the like, there is a concern that the bromine compound may corrode metallic parts of processing machines such as extruders and molding machines, therefore the conditions on usage and the like should be considered. Accordingly, a polyamide resin composition which causes less corrosion of metal than before has been required.
An object of the present invention is to provide a polyamide resin composition which has high heat aging resistance, and is less likely to cause corrosion of metal and deposition of copper.